Automatic sheet stacker

ABSTRACT

A material handling device to stack thin sheet material as it comes from the output end of a suitable upstream process. The sheet stacker has a supporting conveyor surface and laterally spaced therefrom a tray and clutch bar mechanism which is operable to provide the other supporting side to the incoming sheet material. As an individual sheet enters the sheet stacker, it will be supported by the conveyor surface and tray member while at the proper instant the clutch bar will actuate and pull the sheet from the conveyor surface allowing it to fall toward the top of the stack which is being formed between the supporting conveyor surface and laterally spaced tray and clutch bar mechanism.

United States Patent Brookhyser AUTOMATIC SHEET STACKER [72] Inventor: Byron B. Brookhyser, Milton, Wash. [73] Assignee: Weyerhaeuser Company,

Tacoma, Wash.

[22] Filed: March 29, 1971 [2]] Appl. No.: 128,781

[52] US. Cl ..27 1/68 [51] Int. Cl. ..B65h 29/68 [58] Field oi Search ..27l/68 [56] References Cited UNITED STATES PATENTS 2,300,863 11/1942 Bamford ..27l/68 3,328,027 6/1967 Schmidtke ..27l/68 3,367,823 2/1968 Clausen ..'.27l/68 FOREIGN PATENTS 0R APPLICATIONS 919,619 2/1963 GreatBritain ..27l/68 Sept. 12,1972

Primary Examiner-Richard E. Aegerter Attorney-Patrick D. Coogan, John M. Crawford, Stuart A. Heller and Bryan C Ogden 7] ABSTRACT A material handling device to stack thin sheet material as it comes from the output end of a suitable upstream process. The sheet stacker has a supporting conveyor surface and laterally spaced therefrom a tray and clutch bar mechanism which is operable to provide the other supporting side to the incoming sheet material. As an individual sheet enters the sheet stacker, it will be supported by the conveyor surface and tray member while at the proper instant the clutch bar will actuate and pull the sheet from the conveyor surface allowing it to fall toward the top of the stack which is being formed between the supporting conveyor surface and laterally spaced tray and clutch bar mechanism.

6 Claims, 4 Drawing Figures 1 AUTOMATIC SHEET STACKER BACKGROUND OF THE INVENTION manner. More particularly, it relates to the mechanism for stacking relatively flexible thin veneer sheets which are substantially rigid about an axis parallel to veneer travel. I

When the output ofa process is a thin sheet, it is common practice in the art to stack such sheets if they in turn are to be utilized in another subsequent process or if they are to be stored. This is particularly desirable if the rate of production in the sheet process is high thereby leaving little time for the direct utilization of the sheets from a sheet process directly to the next process, whateverfit may be. I

.It is to be noted that the sheet forming process isnot a part of the present invention and may be any suitable ,processffor acting on or with thin sheet material. It is further noted that the sheet material passes through the process such that at the outputend of the process the thin sheet material will be traveling linearly on a suitable conveyor or the like. r I

The present invention is designed to operate on very light pieces of sheet material whichwould normally tend to float slowly toward the ground if they were allowed to fall naturally in a'plane parallel to the ground level. Such a sheet may be, for-example, a piece of core or cross-band wood veneer which is utilized in the manufacture of plywood as one of the interior plies. The normal thickness for such a wood veneer sheet varies from one-sixteenth of an inchto one-half of an inch. The usual plan size for core veneer sheets is on the order of 4 feet by 8 feet thus it will beappreciated that such a large surface area with the total material weight being very small presents a difficult problem for stacking and handling at the output end of a process. The problem with handling core veneer is further complicated by the fact that its grain runs parallel to the shorter dimension and if the grain direction is running perpendicular to the direction of veneer travel it will be appreciated that the veneer sheet will be very flexible about a large plurality of axes which run perpendicular to the direction of travel. Flexibility is even greater when unitized core is to be stacked. Unitized core as is well known to those skilled in the art is of the variety where thin strips of low grade veneers are joined together in any manner known to the art, for example, by taping the strips of veneer together.

In the manufacture of plywood panels, large stacks of veneer sheets are normally employed. When the panels are formed by using the various grades of veneers, each grade (faces, centers, backs, and core) will be available in large stacks to enhance production efficiency. Thus, it is apparent that subsequent to any process which acts on the veneer prior to the formation of plywood panels should provide a stacking procedure. Such processes may be, for example, grading, repairing, or in the case of core veneer, a unitizing process.

Thus, from the foregoing, one object of the present invention is stack thin veneer sheets in a workable pile for subsequent utilization.

Another object of the invention is to provide the abovementioned object in an automatic manner.

Other objects and advantages of the present invention will be realized after taking the following description together with the appended drawings.

SUMMARY OF THE INVENTION Briefly stated, this invention is practiced in one form by providing a pair of spaced apart conveyor surfaces for charging the veneer stacker. One of the conveyor surfaces provides both support and motivating means while the other provides only motivating means. Positioned beneath the motivatingconveyor is a tray which supports the other side of the veneer sheet as it is charged into the veneer stacker. After a veneer sheet is suitably charged and on the proper signal a clutch bar is actuated which secures one long side of the veneer sheet to the rigid tray. The clutch bar and tray then are motivated in a generally horizontal direction away from the conveyor surfaces thus pulling the opposite longer side of the veneer sheet off of itslsupporting conveyor.

This longer side will then begin to fall toward the top of the veneer stack and at this same instant the clutch bar rearward movement is stopped. The tray continues its movement thereby removing itself as a supporting sur face andallowing the other side of the veneer sheet to fall toward the top of thestack. The clutchbar and tray then return totheir original position in order to accept the next incoming veneer sheet.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an isometric view showing both a right and left hand embodiment of the present invention which operate together as a double automatic sheet stacker.

FIG. 2 is an elevation view partially in section showing the principal part of the invention in its ready position. a

FIG. 3 is a'like view showing an individual sheet being pulled from the center supporting conveyor surface. I

FIG. 4 is a like view showing the individual sheet being allowed to fall from the supporting tray and onto the stack.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing and first to FIG. 1 a detailed description of the automatic sheet stacker which is generally indicated as 1, will be given. The automatic sheet stacker 1 is positioned at the output end of a process which acts upon or yields thin sheet material. The output end of the process is indicated in FIG. 1 by way of a plurality of powered conveyor belts 2. The conveyor belts 2 are trained about a plurality of wheels 3 each fixedly mounted to a rotatable shaft 4. Rotatable shaft 4 is of course mounted so as to rotate about two fixed points on a suitable frame. Suitable drive means communicate with shaft 4 to provide the power for turning the conveyor belts 2.

In the embodiment depicted the process upstream of the sheet stacker 1 is one operating on strips of thin wood veneers. The sheet material is unitized thin strips of wood veneer. The unitized wood veneers leave the output end of the process as two large sheets, generally on the order of 4 x 8 feet, with their longer dimensions running parallel to the direction of conveyor travel. It

3 will be further appreciated that wood veneers of this type have their grain running perpendicular to the direction of travel on the conveyor belts 2. In this manner as will be further described later, the thin veneer sheets are relatively rigid about the sheet axis parallel to the direction of travel. It will be appreciated that for the proper operation of the present invention the individual sheet to be stacked must be rigid in the aforementioned manner. It is to be further noted that the embodiment depicted in FIG. 1 is a dual sheet stacker with one being the opposite hand of the other.

The dual sheet stacker embodiment is shown in order to indicate the versatility of the invention. As the individual sheets come from the upstream process, it will be appreciated that they have been clipped to size for proper stacking as well as later use in the subsequent manufacturing process.

' Supporting the primary moving elements of the sheet st'ackerl is a suitable rigid frame comprised generally of two'sections. A lower frame section,;indicated as 5, is comprised of a plurality of vertically extending leg members 6 together with a suitable number of horizontally extending support members 7. The spacing arrangement for the members comprising the lower section of the overallframe is such that there is a pair of material stacking spaces 8 defined thereby. It is, of courseywithin the stacking spaces 8 that the sheet material is accumulated until a sufficient number are stacked and are ready for transportation to another station in the manufacturing cycle. The stacking spaces 8 in physical outline are generally a volume with side dimensions roughly equal to the dimensions of the veneer sheets while the vertical dimension is generally determined by the total number of sheets to be stacked. Positioned beneath the stacking spaces 8 are a pair of vertically adjustable stacking tables 9. Stacking tables 9 are of the scissors lift variety which are well known in the art and are adaptable to be automatically adjustable depending upon the total number of sheets on the table at any time during operation. Stacking tables 9 have a plurality of rollers 10 such that after the total number of sheets are stacked the completed stack can be rolled off of the tables 9 and then readily picked up to be moved to the next stage of manufacture.

The upper section 11 of the overall rigid frame is generally a continuation of the lower section 5 and functions primarily as thesupport means for the operating arms. The plurality of bottom leg members 6 continue upwardly where they become the top vertical frame members 12. Fixedly attached to the vertical frame members 12 are outwardly extending flat support plates 13. Support plates 13 have generally rectangular dimensions and are in a vertical plane which is perpendicular to the direction of sheet travel on the conveyor surfaces. A support plate 13 is fixedly attached to each of the vertical frame members 12 although only one is shown in FIG. 1 on the upper right hand vertical frame member 12. Fixedly attached to the support plates 13 is a front horizontally extending support member 14. Likewise, fixedly attached to the support plates 13 and extending therebetween is a rear horizontally extending support member 15. The support members 14,15 serve two primary functions: firstly, to provide strength and rigidity to the upper section ,11 of the overall rigid frame and secondly, to provide fixed rigid points for the plurality of operating hydraulic cylinders to be described later.

Extending downwardly from and fixedly attached to the support plates 13 are the rear secondary top vertical frame members 17. Although only a single secondary frame member 17 is shown in the downstream lower right hand side of stacker 1 eachsupport plate 13 has such a frame member extending downwardly therefrom. The function of the secondary frame members 17 is, of course, to provide additional vertical support for the weight carried by the plurality of support plates 13 and also to provide a fixed mounting point for a pair of the operating arm members. When describing the operating elements of the instant invention, they will be described by referring to the upper right hand (looking downstream from the belts 2) automatic sheet stacker and it will be appreciated by one skilled in the art that the lower left hand sheet stacker operates and is constructed in exactly the same manner except in an opposite hand.

' Extending between the axially adjacent pair of plates 13 and supported thereby are a plurality of rotatable mounted shaft members generally indicated at 18. Extending downwardly from the shaft. members 18 at either end thereof are a plurality of arm-members generally indicated as .19. Positioned generally at the ends of the arm members 19 and operatively connected thereto is a tray and clutch bar mechanism generally indicated as 20.

At approximately the same vertical point as is the tray and clutch bar mechanism 20 in relation to the bottom or top frame members 6, 12 is a suitable supporting conveyor surface. The supporting conveyor surface for the sheet stacker 1 is a linear continuation of the powered conveyor belts 2 forming the output end of the upstream process. The conveyor surface is comprised of an axially extending endless flat belt 21 which is laterally spaced from the tray and clutch bar mechanism 20 when it is in its rest position a distance which is slightly less than the shorter dimension of the sheet material to be stacked. Endless flat belt 21 is trained over a suitable pair of rotatable wheels 22 and 23 respectively. Wheel 22 is rotatably mounted on the rotatable shaft 4 such that it-is allowed to rotate freely about the shaft 4 and is not turning at the same speed as are the wheels 3. It will of course be appreciated that the endless flat belt 21 could be positioned by other suitable means at its upstream end. The downstream wheel 23 is likewise rotatably mounted although not on a laterally extending shaft. A horizontally extending beam member 24 traversing the distance between the two laterally spaced downstream leg members 6 at a vertical position slightly below the vertical position of the tray and clutch bar mechanism 20 provides a portion of the mounting means for the downstream wheel 23. In addition to providing lateral and vertical support the horizontal beam member 24 has attached to it a suitable mounting bracket 25 which in turn supports the rotatably mounted downstream wheel 23.

Positioned laterally opposite the endless flat belt 21, with the stacking space 8 extending therebetween, is another suitably mounted endless flat belt 26 which forms the other motivating part of the overall sheet stacker conveyor surface. The endless flat belt 26 is mounted in such a manner that its bottom surface is in flexible communication with the tray and clutch mechanism 20. This feature will be more fully described later. Endless flat belt 26 is mounted on a pair of rotatable wheels 28 which are in turn fixedly connected to a pair of suitably mounted laterally extending rotatable shafts 29. In the embodiment depicted in FIG. 1 shafts 29 are mounted on the top vertical frame members 12 through a suitable mounting bracket 30. i r

The endless flat belts 21, 26 forming the stacker conveyor surface are driven by any suitable means (not shown) at .the same linear speed. The powered conveyor belts 2 of the output end of the upstream process are driven at a speed slightly less than the overall conveyor surface of the sheet stacker 1. In this manner of course each individual sheet to be stacked will be allowed to be positioned on the sheet stacker conveyor surface, clutched and allowed to drop onto the top of the stack before the next incoming sheet enters the stacker; I I v w. Now-to bedescribed are the operative elements of the present invention which includethe shaft members 18, {arm members 19, and, tray and clutch, bar mechanism 20. Briefly, theshaft members 18'rotate to pivot the arm members 19 which in turnproperly actuate the tray and clutch bar mechanism 20. A single horizontal tray member 31 extends axially between the two top vertical frame members 12. In its first material receiving or rest position. it extends laterally inward on a horizontal plane a distance such that a portion of one of longer sides of an incoming sheet will be supported by a part of the tray 31. Additional details of the tray and clutch bar mechanism 20 may be seen by referring to FIGS. 24. While the flat tray 31 is in a position to receive incoming sheet material it will be noted that the lateral distance between the flat tray 31 and endless flat belts 21 is slightly less than the shorter dimension of an incoming sheet. In this manner one of the longer edges of the sheet material will be supported by the flat tray 31 while the other edge will be supported by the endless flat belt 21. As previously mentioned, the bottom surface of the endless flat belt 26 ispositioned very close to the tray and clutch bar mechanism 20. In FIG. 2 the exact relationship of the flat tray 31 to the incoming sheet material and endless flat belt 26 as well as to flat belt 21 is shown. Since both flat belts 21 and 26 are powered at the same rate of speed and since the bottom surface of belt 26 is allowed to contact the upper surface of the sheet material, each sheet will be motivated axially along the flat tray 31 in a slidable relationship and along flat belt 21 in a continuously supportable manner. More specifically, the opposite edge of the sheet material will be motivated by flat belt 21 and supported thereby while the other edge of the sheet will be supported by the flat tray 31 but motivated axially by the gripping action of the flat belt 26.

Securely attached to the flat tray member 31 are a pair of outwardly extending rigid arm members 32. Each arm member 32 is supported in the proper spacial relationship by a pivotally connected upwardly extended actuating arm member 33. The pivotal connection point 34 is. positioned approximately midway between the inward side of the flat tray 31 and the outward ends of the arm members 32. Supporting the arm member 32 at their outer ends are a pair of pivotally connected rod members 35. Rod members 35 are sized in order to provide both vertical support for the flat tray 31 and a generally horizontal plane throughout the entire operational cycle of the flat tray 31. The pivotal connections 36 for the rod members 35 are laterally spaced from the pivotal connections 34 in order to provide the aforementioned generally horizontal plane for the flat tray 31. The rod members 35 extend upwardly a suitable distance" to a position where they are pivotally mounted at connection points 37 on the secondary top vertical frame members 17.

At the upper ends of the actuating arm members 33 a rotatable actuating shaft 38 is fixedly attached to the arm member 33. Actuating shaft 38 is, of course, one of the shaft members generally indicated at 18. It is suitably mounted so as to be rotatable within the flat support plates 13. The length of eachactuating arm member 33 is such that as the actuating shaft 38 turns the arm member 33 the pivotal connection. 34 will move on an are which closely'approximates a horizontal plane.

Providing the rotational movement to the actuating shaft. 38 is a hydraulic cylinder 39. Cylinder 39 is pivotally connected to the front horizontal support member14. At its opposite end the hydraulic ram 40 is pivotally connected to a dog member 41 which is fixedly attached to the actuating shaft 38. The travel of the hydraulic ram 40 is such, by way of example, to turnthe arm member 33 through an angle of from. 5 to 10 depending upon the lateral distance that the sheet must be pulled before it leaves flat belt21 and falls onto the stack of veneer sheets 42.

To provide the clutching action a single axially extending clutch bar 43 is positioned just above the horizontal flat tray 31. Forming a part of the clutchbar 43 is an axially extendingresilient clutching material indicated at 44. The clutching material44 is a suitable i type such as rubber which when in contact with the sheet material will provide a clutching and holding action. The clutch bar 43 operates through separate although similar motions as compared to the flat tray 31.

A pair of rearwardly extending arm members 45 are securely fixedto the clutch bar 43. Supporting the arm members 45 and clutch bar 43 in their spacial relationship are the upwardly extending clutch rods 46 and the upwardly extending clutch arms 47. As isseen in F IG. 1 the clutch rods 46 and clutch arm members 47 extend upwardly to the shaft member area 18 The clutch rods 46 extend upwardly and are pivotally connected at points 48 to dog members 49 which are in turn fixedly connected to a rotatable shaft 50. Shaft 50 is positioned slightly ahead of shaft 38 and is approximately in the same horizontal plane. Shaft 50 is, as is shaft 38, rotatably mounted in the flat support plates 13. The rotating means for the clutch shaft 50 is a suitable hydraulic cylinder 51 with an actuating ram 52 mounted in such a manner as to cause the clutch rods 46 to move in an up and down motion for its clutch and hold function. The hydraulic cylinder 51 is pivotally mounted through a mounting bracket 53 at the rear horizontal support member 15 and extends toward the clutch shaft 50 where it is pivotally mounted to a generally upwardly extending dog member 54.

The clutch arm members 47 in a like manner provide the rear support for the arm members 45. The clutch arm members 47 extend upwardly and are fixedly connected to a rotatable swing clutch shaft 55 which is mounted concentrically with the tray actuating shaft 38. The embodiment depicted in FIG. 1 shows the swing clutch shaft 55 as being hollow and mounted through bearing means (not shown) such that it will rotate concentrically about the actuating shaft 38. To provide the actuating means for the swing clutch shaft 55 a suitable hydraulic cylinder 56 with its attendant ram 57 is pivotally connected to an upwardly extending dog member 58 which is fixedly attached to the shaft 55. The hydraulic cylinder 56 extends in a generally horizontal direction to a pivotally mounted connection point on the front horizontal support member 14. By allowing the tray actuating arm members 33 and clutch arm members 47 to pivot about the same point, that is, the concentric axis for the actuating shaft 38 and clutch shaft 55, it will be appreciated that the horizontal flat tray 31 and clutch bar 43 will be allowed to move rearwardly in a substantially synchronous motion such that after one side of the sheet material has been clutched it will be pulled from the endless flat belt 21 and its opposite sideallowed to fall toward the top of the stack 42.

OPERATION OF THE INVENTION In describing the operation of the present invention reference is made to FIGS. 2-4 where the stacking sequence'is depicted. As an individual thin sheet is conveyed toward the output end of the upstream process by the powered conveyor belts 2 it will be traveling at a generally slower rate than when it enters the influence of the conveyor surface of the automatic sheet stacker 1. Assuming now that the first sheet on a new stack is to be properly positionedatop stacking table 9, it will be seen that as the sheet reaches the end of the conveyor belts 2 it will be continually supported by the powered flat belt 21 and the horizontal flat tray 31. Of course the side of the sheet supported by the fiat belt 21 is also conveyed while the opposite side is conveyed axially by the bottom surface of the fiat belt 26. As soon as the sheetmaterial travels the full length of sheet stacker 1 a suitable sensing means (not shown) such as an electric eye will actuate the tray and clutch bar mechanism 20. At this position the sheet material will be directly above and properly centered over the material stacking space 8 In FIG. 2 the time in the stacking cycle which is depicted is that where the sheet material has been conveyed fully into the sheet stacker 1 and the sensing means is ready to actuate the tray and clutch bar mechanism 20. The first sequence is hydraulic cylinder 51 opening causing the clutch rods 46 to move downward and bring the resilient clutching material 44 into contact with the side of the sheet material. At a slightly later time the hydraulic cylinder 39 begins to close causing the horizontal flat tray 31 to move rearwardly. In a synchronous manner the hydraulic cylinder 56 is actuated to bring the clutch bar 43 and clutching material 44 rearward in a clutching position with respect to the sheet member and flat tray 31. Hydraulic cylinder 51 will extend further to compensate for the slight downward movement as the clutch bar 43 and flat tray 31 turn fiat through a slight arc.

Referring to FIG. 3 it will be seen that at this point in the cycle the individual sheet has been pulled laterally a sufficient distance to move off the vertical support provided by the endless flat belt 21. Of course, the side that is no longer supported will begin to fall toward one side of the stack 42.

At this instant the other side of the individual sheet must be released so that it may fall to the top of stack 42. While the clutch bar 43 is in its rearmost position the hydraulic cylinder 39 will continue to close causing the flat tray 31 to move further rearwardly. As tray 31 moves further the resilient material 44 holds the side of the sheet in a vertically and laterally fixed position until tray 31 slides out from under the sheet. At this instant the side of the sheet will lose its vertical support and will fall to the top of the stack 42. By halting the lateral movement of each sheet in the aforementioned manner it should be appreciated that each sheet will fall directly on top. of the previously stacked sheet without any lateral movement therebetween.

The actuation of the hydraulic cylinders to return the tray and clutch bar mechanism 20 to its sheet receiving or rest position is then allowed to occur. Hydraulic cylinder 51 closes causing the clutch rods 46 to return to their upper position while at the same time hydraulic cylinder 39 opens causing the flat tray 31 to return to its sheet accepting position as shown in FIG. 2. Cylinder 56 opens causing clutch bar 43 to return to its rest position over the flat tray 31.

While a detailed example of the principal embodiment has been described, it is understood that many changes and modifications may be made in the abovedescribed automatic sheet stacker without departing from the spirit of the invention. All such modifications are intended to be included within the scope of the apended claims.

What is claimed is:

l. A sheet stacker for automatically positioning an individual sheet atop a stack comprising:

a supporting conveyor surface for axially conveying and supporting an incoming sheet,

a laterally spaced supporting tray, generally in the same horizontal plane as is said supporting conveyor surface,

a clutch bar positioned above said supporting tray,

means to motivate said sheet axially along the top of said supporting tray,

means to motivate said supporting tray laterally away from said conveyor surface,

means to motivate said clutch bar to engage said sheet with said tray and then travel through a portion of said lateral movement of said tray thereby removing said sheet from said supporting conveyor and said tray, and frame means to support said sheet stacker.

2. The sheet stacker as in claim 1 further including a stacking table positioned laterally between and beneath said supporting conveyor and said supporting tray.

3. The sheet stacker as in claim 1 in which said clutch bar is comprised of resilient clutching material.

4. The sheet stacker as in claim 1 in which said sheet motivating means includes an endless flat belt positioned adjacent said clutch bar and adapted to be in driving communication with the top of said sheet as it enters said stacker.

5. The sheet stacker as in claim 1 in which said tray motivating means includes:

an axially extending actuating shaft member rotatably mounted in said frame means and positioned vertically above said tray,

at least two actuating arm members extending downwardly from said actuating shaft member and connected to said tray, and

means to rotate said actuating shaft such that said actuating arms move the tray laterally in a sequential manner away from and toward said supporting conveyor surface- 6. The sheet stacker as in claim 1 in which said clutch bar motivating means includes:

an axially extending clutch shaft rotatably mounted in said frame means and positioned vertically above said clutch bar and laterally from said actuating shaft member,

at least two clutch rods extending downwardly from said clutch shaft and pivotally connected to said clutch bar,

an axially extending swing clutch shaft rotatably mounted in said frame means and positioned concentrically with said actuating shaft member,

at least two clutch arm members extending downwardly from said swing shaft and connected to said clutch bar,

means to rotate said clutch shaft such that said clutch rods move said clutch bar sequentially to its engaged and disengaged position with said sheet and tray, and

means to rotate said swing clutch shaft such that said clutch arm members move said clutch bar in its engaged position through a portion of the lateral movement of said tray away from said supporting conveyor surface. 

1. A sheet stacker for automatically positioning an individual sheet atop a stack comprising: a supporting conveyor surface for axially conveying and supporting an incoming sheet, a laterally spaced supporting tray, generally in the same horizontal plane as is said supporting conveyor surface, a clutch bar positioned above said supporting tray, means to motivate said sheet axially along the top of said supporting tray, means to motivate said supporting tray laterally away from said conveyor surface, means to motivate said clutch bar to engage said sheet with said tray and then travel through a portion of said lateral movement of said tray thereby removing said sheet from said supporting conveyor and said tray, and frame means to support said sheet stacker.
 2. The sheet stacker as in claim 1 further including a stacking table positioned laterally between and beneath said supporting conveyor and said supporting tray.
 2. The sheet stacker as in claim 1 further including a stacking table positioned laterally between and beneath said supporting conveyor and said supporting tray.
 3. The sheet stacker as in claim 1 in which said clutch bar is comprised of resilient clutching material.
 4. The sheet stacker as in claim 1 in which said sheet motivating means includes an endless flat belt positioned adjacent said clutch bar and adapted to be in driving communication with the top of said sheet as it enters said stacker.
 5. The sheet stacker as in claim 1 in which said tray motivating means includes: an axially extending actuating shaft member rotatably mounted in said frame means and positIoned vertically above said tray, at least two actuating arm members extending downwardly from said actuating shaft member and connected to said tray, and means to rotate said actuating shaft such that said actuating arms move the tray laterally in a sequential manner away from and toward said supporting conveyor surface.
 6. The sheet stacker as in claim 1 in which said clutch bar motivating means includes: an axially extending clutch shaft rotatably mounted in said frame means and positioned vertically above said clutch bar and laterally from said actuating shaft member, at least two clutch rods extending downwardly from said clutch shaft and pivotally connected to said clutch bar, an axially extending swing clutch shaft rotatably mounted in said frame means and positioned concentrically with said actuating shaft member, at least two clutch arm members extending downwardly from said swing shaft and connected to said clutch bar, means to rotate said clutch shaft such that said clutch rods move said clutch bar sequentially to its engaged and disengaged position with said sheet and tray, and means to rotate said swing clutch shaft such that said clutch arm members move said clutch bar in its engaged position through a portion of the lateral movement of said tray away from said supporting conveyor surface. 